Examples of valve closure systems to which principles of the present invention may be applied are illustrated in commonly owned U.S. patent application Ser. Nos. 10/418,693 and 10/418,691, filed 18 Apr. 2003, which are incorporated herein by reference. The inventive principles may also be applied to various other valve closure systems.
In certain environments, it may be desirable for a valve closure system to be configured such that when installed on an open shut-off valve of a cylinder or container, it is capable of operating only to close the valve. When so configured, such a valve closure system needs to be removed from the valve before the valve can be re-opened. Removal is typically accomplished by attending personnel. Removal of a valve closure system may be inconvenient and/or time-consuming and if the system has appreciable mass, the task of removing it may be burdensome to attending personnel.
In those cases it may be preferable to enable the attending personnel to re-open the valve without having to remove the closure system from the shut-off valve. But when a valve closure system is enabled to open and close a shut-off valve under control of attending personnel, the ability to assure closure of an open valve from a remote location in the absence of attending personnel on the scene may continue to be required, especially where hazardous fluids may be escaping, and assurance of prompt valve closure is needed.